Do pesticides harm bees? Here’s how the evidence keeps piling up

The #bees collected pollen from #apple trees less often and visited flowers less frequently than when they were not exposed to neonicotinoid #pesticides, scientists said.

In this study, 24 colonies of buff-tailed bumblebee (Bombus terrestris) were exposed to thiamethoxam pesticide.

The study involved assembling three groups of bumblebee colonies and exposing two of them to two different levels of the commonly used pesticide thiamethoxam-2.4PPB and 10PPB and then allowing them to #pollinate segregated apple trees.

Bees and other pollinators help to fertilize around seven in eight species of flowering plants, including many #crops. Stanley said that 1 in 3 bites of #food eaten by us belong to crops pollinated by bees. These chemicals are systemic pesticides: Rather than just sitting on the surface of plants, they are absorbed and transported to all kinds of tissues, including nectar and pollen.

Bees are in decline in Europe and North America, which is in-itself a tremendous danger for #agriculture and the ecosystem at large, in which bees and other insects have a key role in #pollination. Moreover, even if the #neonicotinoids aren’t there at anywhere near a lethal dose, they can still have an impact on insect behavior. Their monitoring of tagged honeybees in the wild suggests bees foraging around treated crops die off at a faster rate than normal. In this new effort, the researchers looked instead on the possible impact on pollination by bees exposed to one type of pesticide, instead of the impact on the bees themselves. Here we show the first evidence to our knowledge that pesticide exposure can reduce the pollination services bumblebees deliver to apples, a crop of global economic importance. They didn’t expose the third group to any pesticides at all. One group was exposed to 2.4 parts per billion; another at 10 parts per billion. However, its use is still permitted in the U.S.

Another study published this week indicated that wild #honey bees compensate for losses due to exposure to neonicotinoids by generating more female workers.

A new study carried out by researchers from the Royal Holloway University of London, the University of Reading, England and the University of Guelph, Canada suggests that use of neonicotinoid pesticides harms the abilities of bumblebees to pollinate apple trees, thus affecting the quality of the fruit and farmers’ crop yields. However, this means they produce fewer breeding males which could pose a long-term risk to colonies.